Wastegate actuator has 2 ports on top, a small one and a big one.

[Grubby]

The turbo is an A/R 42. I know what the big port does (applies boost psi to wastegate actuator diaphragm), but why the small one right next to it? I know that so called "dual port actuators" have a port on top of the diaphragm and one under the diaphragm to hold boost, but mine has a big and small on the top, side by side. The compressor housing has a large and a small port to correspond to the WG ports, but both are on the compressor housing: the little port is NOT on the inlet flange as i've seen on other d24t garrett turbos, which is why I am wondering about the routing of lines. The large port is by the compressor exit (pressure side), and small is one on the curve of the comp. housing. Both would be under pressure in a boost situation. I am guessing this config might be to smooth out the boost curve? I will post a pic, soon, but if someone knows this turbo, and can confirm my planned routing of the lines, please advise. That routing would be: small port on housing to sm. port on WG, large to large accordingly.
Thanks!

[Grubby]

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Just want some confirmation on hose routing: small port on comp. to sm. on wg actuator, large port on comp. to large port on wg actuator, right?
What is the reason there are 2 ports when both are pressure?
Thanks!

[heavyequipment]

Looking at mine, it seems that the big hose supplies boost pressure to the actuator, while the small one vents it, supplying a reference to the other side of the diaphragm that equals the pressure at the turbo inlet. (If that's not right, I'd appreciate an explanation...)

[Jason]

If both ports go to one side of the diaphram, you need to cap one off. I'm assuming if you blow into one of the ports, air would just blow out of the other one. I don't know what that turbo is stock for, but most likely the second port went up to a boost controller that would bleed off pressure to controll boost. The two ports on the turbo may have just gone to different areas on the engine, one to the waste gate, and the other to a sensor, possibly tied in with the boost controller, who knows. Shouldn't really matter if you use the large or small port. Whatever one is left just cap, and the same goes for the port on the turbo, unless you want to run a seperate line up to a boost gauge, or whatever.

Jason